This invention relates generally to conveyor systems, and in particular to the induction section of a conveyor sortation system.
The induction section of a conveyor system generally refers to the portion of the conveying system in which articles are inducted, or initiated, into the conveying sortation system. The induction section typically performs the function of providing the proper gaps between packages, or other articles traveling on the conveying system, so that the packages can be sorted for proper distribution. The gapping of the articles affects the throughput of the conveying system, which is often a factor of high commercial significance. By reducing the gaps between articles on the conveying system, the number of articles that can be placed on the conveying system at a given time is increased. By being able to place more articles on the conveying system at a given time, more articles are moved over a given time period, thus increasing the throughput of the conveying system.
The gapping of the articles also affects the sortation functions of the conveying system. Where the conveying system functions to sort the articles being conveyed, prior art conveying systems have often used pusher shoes or other diverting means to push the articles off of a main conveyor onto one or more branch conveyors. In order for these pusher shoes to sort the packages correctly, it is important that sufficient space be provided between articles so that the pushers do not inadvertently push against another article while they are in the process of diverting a second article.
The sortation functions of the conveying system therefore weigh in favor of providing a certain amount of gapping between articles while the throughput considerations weigh in favor of reducing this gapping to as small a space as possible. The induct portion of the conveying system should be able to consistently and accurately produce gaps that were just large enough to accommodate the gapping requirements of the sortation section of the conveying system as often as possible.
The creation of gaps in prior art conveying systems may suffer because these prior art conveying systems are not able to determine the position of articles on the conveyors with sufficient accuracy. For example, in some prior art conveying systems, the position of the article is determined by sensing the passing of the article by a single photo-detector positioned alongside the conveyor. As the article moves past the single photo-detector, its position is determined how far the conveyor belt had moved since the article had been detected. Determining how far the conveyor belt had moved is often carried out by way of an encoder that measured the amount of rotations of the motor that powered the conveyor belt or one that measures movement of the conveyor belt directly. Due to measurement inaccuracies, slippage, and other factors, this calculation of the article's position on the conveyor has a significant uncertainty. This uncertainty of the article's position on the conveyor makes controlling the created gaps in prior art induct systems difficult.
In light of the foregoing disadvantages of the prior art, the need for an induct system that improves the accuracy and consistency of the created gaps between articles can therefore be seen.